FIG. 1 depicts a prior art wireless communication system. The system 100 is comprised of a communications tower 102 at the top of which is an antenna 104. Radio frequency signals 106 emanate from, and are picked up by the antenna 104 in the course of providing two-way wireless communications to compatible communications devices, such as a conventional cellular telephone 108 in a motor vehicle 110 or which can be carried about by a person, not shown.
In FIG. 1, the cellular telephone 108 in the vehicle 110 provides both two-way voice communications to users of a motor vehicle 110 and telematics data services to the motor vehicle 110. A telematics data service is a wireless data connection between sensors located on a vehicle 110 and a service provider that monitors the state of such sensors via a connection provided by a cellular telephone or other compatible wireless communications network. The General Motors ON-STAR™ system is an example of a telematics data service.
The cellular telephone 108 maintains communication with a cellular network, not shown, by the radio frequency signals that are exchanged between the cellular radio 108 and the antenna 104 so long as the cellular radio 108 is within a geographic coverage area 110 or cell within which radio communications with a cellular radio 108 can be maintained.
When the cellular radio 108 is powered down, it sends a power-down or de-registration message 112 to a cellular network controller, not shown, via the tower 102 service the cell 110 within which the cellular telephone 108 is operating. When the cellular system receives the power-down or de-registration signal 112, the cellular system acknowledges the power-down message 112 by the transmission of an acknowledgment message or “ACK” message, which when received by the cellular telephone 108 notifies the telephone 108 that the power-down sequence was received by the network. On the other hand, it a response to a power down, de-registration message 112 is not received by the cellular telephone 108, it will subsequently power-up in an indeterminate state vis-a-vis the network. The network might not know whether the cellular telephone 108 is “present” on the system or within the cell 110 or otherwise reachable. Among other things, text messages transmitted to the telephone 108 while it was powered down (off) might be sent to the telephone 108 by the network without the network being able to determine whether the messages were actually received. A method and apparatus for avoiding the ambiguity and operating state when a cellular radio powers-down but does not receive an acknowledge signal from the network would be an improvement over the prior art.